Characterization of Products from Chloroform-Extracted Triassic Chang 7 Oil Shale Generated by Semiopen Pyrolysis

A semiopen hydrocarbon generation thermal simulation experiment was conducted on the Chang 7 shale after chloroform extraction. The characteristics of expelled, retained, and total generated oils were analyzed. The influence of the free hydrocarbons (S-1) was ruled out after extraction, and the kerogen hydrocarbons (S-2) dropped nearly 92.5%, which is the main source of oil generation. The oil generation of the Chang 7 shale was divided into three stages: 300-320 degrees C is the slow hydrocarbon generation stag; which is mainly the initial cracking of kerogen, and the amounts of expelled and retained oils are small; 320-360 degrees C is the rapid hydrocarbon generation stage, which is mainly the second cracking of kerogen, resulting in a rapid increase in expelled, retained, and total generated oils; and 360-420 degrees C is mainly the cracking of the retained oil generated in the early stage. The cumulative total generated oil before 360 degrees C is larger than that generated after 360 degrees C, which suggests that a large amount of oil was generated before 360 degrees C; however, this part of the oil is mainly the retained oil. At this stage, as the pyrolysis temperature continues to rise, C14+ in the retained oil generated in the early stage begins to crack. C6-14 and C14+ have a correlation similar to the "zero-sum game", suggesting that there is an inherent transformational relationship between them. A semiopen hydrocarbon generation thermal simulation experiment was first conducted on the chloroform extraction of the Chang 7 shale. This study confirms that the increase in pyrolysis temperature (>360 degrees C) is beneficial to generating more expelled oil, which has practical implications for the in situ conversion of shale oil.